The present invention relates to an apparatus for electroplating a strip of metal of a relatively low electric conductivity, for example, a stainless steel with gold.
Many contact elements for electronic devices are conventionally made of Phosphor Bronze or Beryllium Bronze, which are excellent in the electric conducting property. Recently, the need has arisen to use such a contact element for communicating a minimum electric current, which requires such contact elements to provide mechanical resilience as well as electric conductivity. Thus, contact elements of Phospor Bronze or Beryllium Bronze must be formed to be relatively thick.
Stainless steel, as is well known, is excellent in mechanical resilience. Therefore, it is advantageous for contact elements for the above-mentioned use to be made of a relatively thin stainless steel electroplated with gold, since contact elements made of stainless steel may be formed in a small size. Relatively thin stainless steel is obtained from hoop or band steel. However, difficulties arise when stainless steel is gold plated, because the gold must be plated only on portions of the stainless steel and those portions should be as small as possible due to the cost of gold; and wherever the gold is plated, it must be plated at a uniform density. However, it is difficult to plate gold uniformly because stainless steel has a greater electric resistance as compared to copper. Continuous electroplating of stainless steel with gold over a long term has never been accomplished, because of the high electric resistance of stainless steel. If the cathode electrode is connected to the stainless steel outside of the electroplating solution, as in the conventional method, the electric current does not reach the portion of the steel in the solution away from the electrode connecting point, but reaches only the portion near the point where the cathode electrode is connected. If the cathode electrode is connected to the stainless steel within the electroplating solution, gold precipitation concentrates at the connecting points, where the electric voltage is almost completely consumed causing the electric voltage fed to the stainless steel to be reduced.